Elongation factor three (EF-3) is a translational factor present in the fungal kingdom but appears to be absent from higher eukaryotes. Preliminary investigation by Western blot analysis and PCR amplification indicate that Aspergillus also carries an EF-3 homologue. The proposed project is to isolate and sequence the DNA of the homologue of EF-3 in the medically important fungus Aspergillus. Accomplishing this goal will serve the purpose of confirming the presence of an EF-3 homologue in Aspergillus and allow comparison with known fungal homologues. This comparison should provide information regarding the organization of EF-3 genes in Aspergillus, (since most Aspergillus genes, in contrast to the known fungal EF-3 sequences, contain introns), and should further confirm and characterize a highly conserved protein motif: GEDLCNCEFSLAYGAKILLN found in previously sequenced EF-3 genes. At present the function of this motif is unknown, yet its almost 100% degree of conservation in the three fungal proteins and in the one non-fungal sequence, that of the eukaryotic green algal virus CVK2, suggests that it is of fundamental importance for the functional activity of the EF-3 protein. Aspergillus infection is a major threat to the survival of patients whose immune systems are impaired by chemotherapy or radiation therapy for cancer, patients with immuno-suppressive drugs for tissue, organ and bone-marrow transplantation and patients with diminished function due to progression of AIDS. Current microbiological and immunological techniques are inadequately sensitive to detect Aspergillus infection before it is so advanced that the patients will not respond to therapy. Isolation and sequencing of the EF-3 gene from Aspergillus may provide information facilitating development of a PCR based assay for Aspergillus infection. Successful characterization of a fungal EF-3 homologue in Aspergillus is an essential component for this type of diagnostic tool allowing detection of Aspergillus infection early enough to provide therapy and enhance patient survival. There is tentative evidence for an EF-3 homologue in the protozoan parasite Entamoeba histolytica and possibly in Tetrahymena. Further research in this project will seek to confirm the presence of EF-3 in protozoa. EF-3 is already considered an attractive target for anti-fungal drugs. If the involvement of this extra factor in translation included parasitic protozoa, drugs developed against fungal EF-3 proteins might also have anti-protozoal activity.